Showy Crotalaria (Crotalaria spectabilis)

Plant Snapshot

Common Name: Showy Crotalaria
Latin Name: Crotalaria spectabilis
Hardiness Zones: USDA zones 9–11 as a perennial; often grown as an annual in cooler areas. In colder zones plants die with frost and are treated as annuals. In warm zones plants can persist and spread
Typical Height: 2–5 ft (60–150 cm) tall
Typical Spread: 1–3 ft (30–90 cm) spread
Bloom Period: Summer to fall in warm climates; timing varies by region
Soil Preferences: Prefers well drained soils and tolerates poor, sandy soils. Avoids waterlogged conditions. Performs on neutral to slightly acidic pH
Light Preferences: Full sun to light shade; full sun gives best flowering
Toxicity: Contains pyrrolizidine alkaloids that can cause liver damage in livestock and humans if ingested. Seeds and foliage are of greatest concern. Handle with care and prevent access by grazing animals
Propagation: Mainly by seed. Sow directly after last frost or start indoors. Plants readily self seed and can spread where climate is favorable

Key Facts

Herbaceous annual or short lived perennial in the pea family
Bright yellow pea like flowers held in terminal racemes
Commonly used as a green manure and cover crop in warm regions
Can self seed and form dense stands where climate is suitable
Contains pyrrolizidine alkaloids that can cause liver damage if ingested
Prefers full sun and well drained soils
Propagated mainly by seed

Showy Crotalaria is a bright yellow flowering legume valued for ornament and as a green manure. It thrives in heat and is usually grown from seed, but can self seed and persist where winters are mild.

Identification

Herbaceous annual or short lived perennial in the pea family that typically reaches 2 to 5 feet tall and spreads about 1 to 3 feet. Plants bear bright yellow pea like flowers in terminal racemes and form clumps that can become dense when many seedlings establish.

Best uses and where to grow

Use as a summer bedding plant for bold yellow display and as a green manure or cover crop in warm regions. Best in full sun where flowering is most prolific. In frost free USDA zones 9 to 11 it may persist year to year; in colder areas treat it as an annual.

Planting and spacing

Propagate mainly by seed and sow directly after the last frost or start seed indoors for earlier bloom. Space plants roughly 12 to 36 inches apart to match the typical 1 to 3 foot spread and allow airflow to reduce disease and limit self seeded thinning later.

Water and soil

Prefers well drained soils and tolerates poor sandy sites while avoiding waterlogged ground. Poor drainage leads to root decline and reduced vigour. Full sun gives the best flowering though light shade is tolerated in very hot locations.

After flowering and spread control

Plants readily set seed and can form dense stands where climate is suitable. Remove seedpods before they mature to limit volunteer seedlings and pull young volunteers promptly. Check local invasive species lists before planting because it is listed or regulated in some regions.

Toxicity and safety

Contains pyrrolizidine alkaloids that can cause liver damage in livestock and humans if ingested. Seeds and foliage are of greatest concern. Keep plants out of grazing areas and prevent access by pets and livestock while verifying regional toxicity guidance with local veterinary or poison control sources.

Frequently asked questions

How fast does Showy Crotalaria grow?: It grows quickly in warm, fertile sites and can reach the typical 2 to 5 foot height within a single growing season where conditions are favorable.
Is Showy Crotalaria invasive?: It can self seed and form dense stands. Regional invasiveness varies so check local noxious weed lists before planting.
Is it poisonous to livestock?: Yes. The plant contains pyrrolizidine alkaloids that can cause liver damage and photosensitization in grazing animals.
Can I grow it in cooler climates?: In colder zones treat it as an annual and sow after the last frost. It persists as a perennial only in warm, frost free zones such as USDA 9 to 11.
How do I prevent it from spreading?: Remove seedpods before they dry and disperse and pull volunteer seedlings. Avoid planting where native vegetation could be outcompeted.